Keratin Treatment For Thin Hair: Side Effects And Alternatives

Learn if this treatment is the best choice for your hair and alternatives to try.

Reviewed by Tiffany Young, Certified Trichology Practitioner
Written by Anjali Sayee
Edited by Eshna Das, Certified Skin Care Coach
Fact-checked by Krati Darak, Certified Skin Care Coach  • 

No, keratin does not thicken hair. Thus, it may not be a good hair treatment for thin hair. But it does protect it from damage. Keratin does wonders for the hair. But what is the verdict on undergoing keratin hair treatment for thin hair? Thin hair gets greasy quickly and ends up looking flat and dull. This treatment might make your thin locks look flatter and even more lifeless. But if keratin strengthens hair, shouldn’t it increase your hair thickness, making thin hair look fuller? Learn if keratin treatments improve hair thickness, their possible risks, and the available alternatives. Keep reading.

Does Keratin Thicken Hair?

Smooth, healthy, and frizz-free hair
Image: Shutterstock

No, keratin does not thicken hair, but it protects it from damage. Keratin products are mainly used to smoothen hair out. Human hair consists of hard keratins that contain 65-95% of proteins, 1-9% of lipidsi  XFatty substances that regulate what enters and exits the body’s cells, store energy, absorb vitamins, and produce hormones. , 3% of melanini  XA natural pigment found in organisms that originates from the amino acid tyrosine, which provides color to hair, skin, and eyes , and a few other minor compounds (1). Keratin is formed by the epithelial cellsi  XCells present on the inside of your body and on its surface, like in and around the blood vessels, organs, and on the skin during the hair growth phase. It protects the epithelial cells from physical damage.

However, protein hydrolysates (protein bonds already broken into dipeptides and tripeptides), like hydrolyzed keratin, have low molecular weights and can protect hair from environmental and chemical damage (2). Keratin hydrolysates are obtained from nails, wool, horns, and feathers of animals. Vegetable options for keratin hydrolysates include soy, wheat, and corn, though they are not as effective as the keratin obtained from humans and animals.

When keratin hydrolysates extracted from feathers were placed on cuticle scales, they sealed the cuticles and protected the hair from heat damage. These hydrolysates also enhanced hair color and shine. The positive charges of protein hydrolysates neutralize the negative charges of damaged hair. They reduce any interfiber frictioni  XFriction caused due to the overlapping of hair fibers that happens on the cuticles of hair strands and frizz. In the following section, we will look into the keratin treatment process in detail.

What Is The Keratin Treatment Process?

The Keratin Treatment uses a flat iron to smoothen out tresses
Image: Shutterstock

The keratin treatment was started in Brazil. It uses a blend of formaldehyde solution, conditioners, and keratin hydrolysates to smoothen and straighten hair. Lately, this formaldehyde solution has been replaced by formaldehyde releasers, which are safer alternatives. The process involves saturating your hair with a formaldehyde solution, drying it out, and using a flat iron to lock your hair in a straight position (2). However, the chemicals used for smoothing hair are not as strong as those used in hair straightening treatments. This makes the keratin treatment less damaging (though it is not ideal for all hair types).

Keratin smoothens out rough and frizzy tresses to make them silky smooth
Image: Shutterstock

The hair is straightened when water breaks the hydrogen bonds of the keratin molecule. It is then blow-dried straight (a flat iron can also be used). The newly redesigned keratin remains in this shape as the formaldehyde crosslinks the keratin filaments in a perfect alignment (2).

protip_icon Quick Tip
Opt for a sulfate-free shampoo and conditioner after a keratin treatment as sulfates may interfere with the treatment and damage your hair.

Though the keratin treatment process is relatively less damaging, it may cause certain side effects.

Side Effects Of The Keratin Treatment

Woman worried about her hair
Image: Shutterstock
  • Research shows that the keratin extracted from plants cannot match that produced in humans. Hence, it cannot restore or treat damaged hair (2).
  • The formaldehyde used in the keratin treatment is a classified carcinogeni  XAny substance or compound with the potential to cause cancer in the living tissues of humans or animals by the World Health Organization (3). However, the potential carcinogenic effects of formaldehyde are yet to be thoroughly studied.
  • Ever since its invention, every salon in Brazil was performing the Brazilian Keratin Treatment (BKT). Consumers complained of burning eyes, mouth, nose, and a strong smell. Though the ingredients used today are based not on formaldehyde but formaldehyde-releasers, like methylene glycol or glyoxylic acid, even these substances can release formaldehyde when heated by a blow-dryer or a hot iron (4).
  • Even professional hair smoothing treatments labeled formaldehyde-free can produce formaldehyde concentrations that meet or exceed current occupational exposure limits.
  • Some believe that the formaldehyde concentrations in BKT products may exceed the recommended levels and serve as a health hazard.
  • A study showed that formaldehyde caused a new onset of asthma (5).
  • The keratin treatment process requires the flat hot iron to be applied to the hair surface 15 to 20 times on the same spot. This process can be quite aggressive and damage the integrity of the hair fiber proteins (2).

The good news is there are alternatives to the keratin treatment process. Keep reading to know more about them.

Keratin Treatment Alternatives

Woman using hair serum on hair.
Image: Shutterstock
  • You may opt for hair products containing keratin. Shampoos, conditioners, smoothing serums, and masks that contain protein hydrolysates can help smooth hair and prevent frizz and interfiber friction.
  • You can also use shampoos that have biotin as an ingredient. The biotin helps the hair shafts appear fuller.
  • Hair fiber sprays can be used to give hair a thicker appearance. These hair fibers are made with keratin that is similar to human keratin. The hair fibers are usually positively charged and get attached to the negatively charged natural hair strands. They can be sprayed on and washed off.
  • Having a hair care regimen is another good alternative. Oil and massage your hair and scalp regularly. Use hair masks to strengthen hair and prevent hair thinning and help with hair repair. Stop using heating tools too often.
  • Have a healthy and balanced diet. A diet rich in protein, fiber, vitamins, and minerals can boost hair health. You can also take supplements for adequate nutrient intake.
  • Use products with keratin to style your hair. These protect your hair from heat and chemical damage. They can also enhance hair shine and color.
protip_icon Quick Tip
Japanese hair straightening and cysteine smoothing treatmenti  XA hair treatment process that uses cysteine, an amino acid, to smoothen and strengthen the hair strands are good alternatives for keratin treatment.

Infographic: Side Effects Of Keratin Treatment On Thin Hair + 5 Alternative Treatments

Despite its increasing popularity, keratin therapy may not suit all hair types. While it successfully reduces hair damage and provides the hair with a sleek and shiny appearance, a few side effects must be kept in mind. Check out the infographic below for better awareness of the keratin treatment and 5 alternative treatments that you can choose.

side effects of keratin treatment on thin hair + 5 alternative treatments (infographic)

Illustration: StyleCraze Design Team

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Download Infographic in PDF version

Getting keratin treatment done on thin hair may leave it more flat and damaged. This treatment uses formaldehyde or formaldehyde resin to straighten your hair, which leaves it more prone to damage. It is better to use hair care products that contain keratin. Keratin protects the hair from any damage. You can look for animal-derived keratin hydrolysates or vegetable hydrolysates made from soy, corn, and wheat. You can also use hair styling products like leave-in conditioners. Remember to pair these products with a healthy diet that can boost your protein production and make your hair healthier.

Frequently Asked Questions

Does keratin cause hair thinning?

Yes, keratin treatment is a harsh procedure and may cause hair loss and thinning.

Does keratin treatment give volume?

No, on the contrary, it makes hair flatter by taming volume, curls, and frizz.

How long does keratin treatment for thin hair last?

Keratin treatment may last up to 5 or 6 months.

Can we oil hair after keratin treatment?

You should not oil your hair for at least 3 days (maybe more in some cases, depending on the type of keratin treatment) after keratin treatment. After that period, you may oil your hair with products recommended by your stylist.

Can I comb my hair after keratin treatment?

No, not immediately. It is better to wait at least 3 days before combing your hair if it is tangled up after a keratin treatment.

Key Takeaways

  • Keratin treatment gives your hair extra shine, helps keep it healthy, and improves heat protection.
  • The treatment smoothens and straightens your hair with a mixture of formaldehyde solution, conditioners, and keratin hydrolysates.
  • Keratin-based shampoos, conditioners, and hair masks can make your hair smoother and more manageable.

You can opt for a keratin treatment to get thicker, healthier, and shinier hair in no time, but is it suitable for thin hair? Watch this video to know more.


Articles on StyleCraze are backed by verified information from peer-reviewed and academic research papers, reputed organizations, research institutions, and medical associations to ensure accuracy and relevance. Read our editorial policy to learn more.

    1. Human Hair Keratin and Its-Based Biomaterials for Biomedical Applications,
    2. Hair Cosmetics: an Overview,
    3. Hair Smoothing Treatments: Perceptions and Wrong Practices Among Females in Saudi Arabia,;year=2019;volume=23;issue=1;spage=20;epage=23;aulast=Algarni
    4. Hair-Smoothing Products That Release Formaldehyde When Heated,
    5. Asthma from Hair Straightening Treatment Containing Formaldehyde: Two Cases and a Review of the Literature,
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